1. Field of the Invention
This invention is related in general to the field of counter-rotating engines and, in particular, to a novel configuration for a rotary engine that enables the advantageous counter-rotation of the engine""s shaft and block for suitable applications.
2. Description of the Related Art
All internal combustion engines share the characteristic of transforming the pressure generated by the combustion of a fuel into the useful rotation of a shaft. Piston engines cause the rotation of the shaft by expanding the combustion gases between a stationary cylinder and a movable piston connected to the shaft. Turbine engines similarly utilize the expansion of combustion gases between an array of stationary blades and a corresponding array of rotatable blades attached to an output shaft.
Thus, in typical applications the engine is firmly mounted on a support structure and delivers power to a useful load by means of a rotating output shaft. In aviation applications, the engine is attached to the body of the aircraft and a propeller is mounted on the shaft to produce propulsion. As a result of the torque produced by the operation of the engine on the rotating shaft and propeller, an opposite reactive torque is produced on the stationary parts of the engine and the frame of the airplane to which it is attached.
Aviation engineers have long searched for ways to reduce the instability that results from this reactive torque. One way has been to provide two propellers that rotate in opposite directions to produce symmetrical counter-balancing actions and reactions, either in twin-engine or in single-engine configurations. The twin-engine solution can obviously be implemented with any kind of power plant, including reciprocating-piston engines, simply by providing opposite directions of propeller rotation in each engine.
The single-engine solution to achieving counter-rotating propeller propulsion has been explored in aviation technology by allowing both the rotation of the crankshaft and the counter-rotation of the cylinders of a reciprocating-piston engine. This approach involves counter-rotating structures (engine block and crankshaft) which support two propellers rotating in opposite directions to each other, which results in a greater amount of propelling force and a substantially perfect torque balance. To that end, the combustion-chamber/crankcase configuration of internal-combustion engines has been modified in various manners over the years to attain a well balanced counter-rotating propeller system. See, for example, the solutions provided by Escher (U.S. Pat. No. 1,052,658), Conill (U.S. Pat. No. 1,151,568), Exel (U.S. Pat. No. 1,561,424), Hockney (U.S. Pat. No. 2,336,787), Muffly (U.S. Pat. No. 2,419,787), Olcott (U.S. Pat. No. 2,838,123), Conkle (U.S. Pat. No. 3,554,666), Keever (U.S. Pat. No. 6,193,189), and Canton (French Patent No. 397,499).
These patents describe four-cycle reciprocating-piston engines designed to balance opposite torques internally either by means of two counter-rotating output shafts connected to multiple crankshafts originating from a stationary enclosure, or by a rotating crankshaft cooperating with a counter-rotating combustion-chamber enclosure. The various solutions disclosed in these patents involve complicated engine mounting, inlet/exhaust porting and lubricating systems, all of which greatly affected their practical implementation.
The very nature of four-cycle reciprocating-piston engines, which comport the use of cranks in the output shaft and pistons traveling radially with respect to the axis of rotation of the crankshaft and cylinders, produces an inherently heavy and precarious structure that requires bearing supports at both ends of the engine. In addition, because each piston operates radially from a corresponding crank in the output shaft, access to the combustion chamber for fuel delivery is necessarily limited to the distal end of each cylinder, which presents very difficult problems during rotation of the cylinders. Lubrication is similarly complicated by centrifugal-force effects that tend to cause the accumulation of oil below each piston and away from the crankshaft. Accordingly, no counter-rotating engine has been successfully implemented commercially using four-cycle reciprocating-piston configurations in spite of the theoretical advantages provided by this concept.
Since reciprocating-piston engines are designed to operate at substantially the same rpm required for proper propeller performance, no additional transmission device is required between the engine and the propeller. On the other hand, rotary-piston engines, which afford many well-known advantages with respect to reciprocating-piston engines, operate at speeds 2 to 4 times higher than propeller operating speeds. Therefore, rotary engines are less satisfactory for propeller-driven aircraft propulsion because they require additional transmission mechanisms to convert engine operating speeds to propeller operating speeds. The additional weight and complexity of a transmission have greatly reduced the performance advantages of rotary-piston engines and, therefore, also their usefulness for normal propeller-driven aircraft applications.
No attempt has been made to convert a rotary-piston engine to a counter-rotating dual propeller system. U.S. Pat. No. 1,594,035 (Bailey) and No. 1,841,841 (Munn) describe unique rotary-type engines configured to allow the combustion chamber enclosure and rotor mechanisms to rotate about a stationary crankshaft. Neither patent describes a propulsion system that balances opposite torques internally. U.S. Pat. No. 1,461,436 (Messina) describes a rotary engine as a propulsion device for a craft that relies upon airframe manipulation to counteract the forces of adverse torque caused by the rotary-engine-driven propulsion system. Thus, the Messina patent does not describe a rotary, internal combustion propulsion system that resolves torque internally, either.
Therefore, there is still a need for a better implementation of the counter-rotating propeller approach to solving the dynamic balance problems experienced in aviation and other applications as a result of the torque imparted by a fixed engine on a supporting structure. This invention provides a novel approach based on the recognition that engines that do not require a crankshaft, such as rotary-piston engines, turbine engines, and electric motor engines, may be advantageously mounted on a fixed spindle.
The primary goal of this invention is an engine propulsion system, especially for propeller driven aircraft, that balances opposing crankcase/crank torques internally and thereby transmits no resulting torque to the airframe.
Another objective is a counter-rotating engine wherein the absence of engine components with reciprocating radial motion prevents the accumulation of fluids in engine cavities, which hinders high-speed performance of the engine, as a result of centrifugal forces.
Another goal of the invention is a counter-rotating engine propulsion system, especially for propeller driven aircraft, that requires no additional component for transmission or speed reduction in order to achieve satisfactory propeller operation.
Another objective of the invention is a counter-rotating engine propulsion system, especially for propeller driven aircraft, that can be stably and safely journaled on a single spindle mounted on the frame of the aircraft.
Still another objective of the invention is a counter-rotating engine propulsion system, especially for propeller driven aircraft, that can be fueled and exhausted through internal ports that are fixed with respect to the aircraft""s frame.
Another goal is a counter-rotating engine propulsion system, especially for propeller driven aircraft, that eliminates the need for auxiliary combustion-chamber temperature-distribution apparatus by providing a combustion-chamber enclosure that includes a plurality of internal cooling tubes which, during rotation of the enclosure, cause thermally conductive fluid to evenly distribute combustion chamber temperatures across the entire surface of the combustion chamber.
Yet another goal is a counter-rotating engine propulsion system, especially for propeller driven aircraft, that eliminates the need for auxiliary engine cooling mechanisms by providing a combustion-chamber housing that includes external cooling fins which, during rotation of the housing, cause sufficient air movement across the cooling fins to adequately cool the combustion chamber.
Finally, another goal of the invention is a counter-rotating engine propulsion system, especially for propeller driven aircraft, that eliminates the need for auxiliary combustion-air induction mechanisms by providing channels integral to either the combustion chamber enclosure or the crankshaft which, during rotation, cause combustible air to circulate under pressure into the combustion chamber.
Therefore, according to these and other objectives, one aspect of this invention consists of a counter-rotating rotary-piston engine having an output shaft with a cylindrical inner cavity rotatably mounted on a single support spindle in the frame of an aircraft. The output shaft extends substantially through the length of the engine block, which is suitably journaled on the shaft or the spindle to permit its counter-rotation. Internal combustion power is transmitted to the output shaft by means of an inner rotary piston fixed to the shaft which cooperates in conventional manner with an outer working chamber in the engine block, thereby producing concurrent rotation of the shaft and counter-rotation of the engine block. Dual propellers mounted on the shaft and on the block improve thrust performance, inherently balance the torques and moments of inertia of the two counter-rotating masses, and virtually eliminate any resultant torque to the aircraft.
According to another aspect of the invention, a counter-rotating turbine engine has an output shaft that is similarly rotatably mounted on a support spindle in the frame of an aircraft. The engine block is journaled on the shaft or the spindle to permit its counter-rotation. Turbine power generated by a pressurized fluid is transmitted to the output shaft by means of rotating vanes in the shaft that cooperate in conventional manner with corresponding stationary vanes in the engine block, thereby producing rotation of the shaft and counter-rotation of the engine block. As in the case of the rotary-piston engine, dual propellers are mounted on the shaft and on the block to improve thrust performance, balance the two counter-rotating masses, and virtually eliminate resultant torque.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose but one of the various ways in which the invention may be practiced.